1. Field of the Invention
This invention is related generally to a device for reducing the rate of evaporation from fluid storage basins, and more particularly to a film pump capable of producing a stable monolayer film over large water surfaces with complex surface geometries to reduce evaporation loss.
2. Prior Art
Evaporation from bodies of fluids, such as reservoirs, holding tanks, and the like, can be reduced by covering the fluid surface with a film of a liquid having a lower vapor pressure than the fluid covered. For example, the use of films of cetyl alcohol on the surface of bodies of water to reduce evaporation loss is well known. Likewise, previous inventions have used various methods for application of the film to the water surface.
Australian Patent No. 217,139 to Mansfield discloses a method for reducing the rate of evaporation from a body of water by use of a carder of a fibrous nature such as cotton to which cetyl alcohol or another active material has been applied. The carrier is floated on the body of water so that the active material may spread across the surface of water.
U.S. Pat. No. 2,878,098 to Treloar et al. discloses means for preventing evaporation from reservoirs or the like by use of a plurality of dispensing units anchored around the perimeter of the area to be protected. The dispensing traits are provided with a protective film-forming substance such as cetyl alcohol stored in a supply tank connected to the dispensing unit. In one embodiment, release of the film-forming substance is controlled by wind pressure applied to a wind vane on the dispensing unit. When sufficient wind pressure is applied to the wind vane, a normally closed valve is opened to release the film-forming substance so as to form a film on the surface of the water. In another embodiment, a paddle wheel assembly is used to control the release of the protective film-forming substance from the dispensing unit in response to the amount of water current.
U.S. Pat. No. 3,285,692 to Robertson discloses an apparatus for distributing material to reduce evaporation from water storage basins comprising a hopper in which a block of film-producing material such as hexadecanol is provided, a housing having an assembly of rotating brushes which form small particles of hexadecanol when bristles of the brush assembly come in contact with the solid hexadecanol stored in the hopper, and an outlet connected to the housing for discharging the small particles of hexadecanol from the housing. The brush assembly is rotated at a speed of about 3,000 rpm by an internal combustion engine connected to a spindle on which the brush assembly is installed.
U.S. Pat. No. 3,528,764 to Reiser discloses a method and apparatus for retarding evaporation from water surfaces based on the concept of providing small fragments of an oleaginous material to a stream of water so as to form an emulsion of the oleaginous material and water. The emulsion is then sprayed onto the body of water to be protected preferably by a line of sprayers mounted around the perimeter of the body of water. The sprayers may be activated in response to the wind.
U.S. Pat. No. 4,455,226 to Lahav discloses a method and apparatus for treating the surface of a solar pond with oil. The method involves applying the oil to the surface of the pond, collecting the oil, and purifying the oil with filtration means to remove particles collected from the surface of the pond. The purified oil is then reapplied to further remove debris.
U.S. Pat. No. 3,353,610 to Vidal discloses a liquid film maintaining apparatus for redistributing a protective coating applied to a body of water so as to prevent evaporation. The apparatus includes a plurality of circular float members disposed on the surface of the body of water. A protective film which is already applied to the surface of the water is partially maintained by each member. The portion of the protective film so enclosed is retained on the body of water and generally not displaced by wind current.
These existing methods for applying films to the water surface, because of their dependence on water current or wind for film distribution, have difficulty spreading the film over pools with large or irregular surface geometries. Existing film spreading devices have difficulty spreading alcohols of longer carbon chain length such as eicosanol (C-20) and docosanol (C-22) into an effective film layer because of the higher molecular weight and greater viscosity of these alcohols. Another difficulty with previous devices is that they spread the film material on a water surface previously exposed to the ambient surroundings, which may be contaminated by airborne dust particles or other debris which inhibits the film layer's evaporation-retarding qualities, rather than to a fresh surface of water uncontaminated by airborne debris. Thus it can be seen that there is a need for a new and improved device for the application of a stable monolayer film over water surfaces with large or irregular surface geometries, which is not dependent on water current or wind for film distribution. It is to this need that the present invention is directed.